Democrats had to replace Sen. Al Franken, D-Minn., who resigned after being accused of sexual misconduct. They also picked up a spot with Doug Jones' victory in last month's Alabama Senate race.
The Congressional Black Caucus had been urging Senate Minority Leader Chuck Schumer, D-N.Y., to appoint one of its members to the committee.
"The experience and expertise they bring to the committee will be beneficial for all Americans, especially those disproportionately targeted by the criminal justice system," said Rep. Cedric Richmond, the group's chairman.
Harris is a first-term senator who served as California's attorney general before winning election last year. Booker, a former Newark mayor, has been in the Senate since winning a special election in 2013. He tweeted Tuesday: "It'll be my mission to check awful actions by Trump & Sessions; keep working to advance the cause of reforming our broken justice system; and to bend the arc of history closer toward equal justice for all."
The Senate Judiciary Committee is responsible for conducting hearings and for considering the president's nominations to serve at the Justice Department and on the federal judiciary. The Republican edge on the committee will narrow from 11-9 to 11-10 as a result of the appointments.
Former Sen. Carol Moseley Braun, D-Ill., is the only other African-American to have served on the committee.
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